This work by Rob Hill is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Feel free to use anything that I have created.
Unfortunately, a large number of the worksheets contain images. Most of these are used without any attribution at all, and my efforts to fix this are ongoing.
If you have questions or comments, or if you hold the rights to any images used, please contact me at firstname.lastname@example.org